The response of alfalfa, flax and wheatgrass growth to application of petroleum sludge

The present study was carried out to study the germination and growth capability of three plants including alfalfa (Medicago sativa L.), flax (Linum usitatissimum L.) and wheatgrass (Agropyron elongatum (Host). Beauv) in contaminated soils with petroleum sludge produced by Isfahan Oil Refinery in a greenhouse experiment. The air-dried petroleum sludge sample was added to an uncontaminated soil at ratios of 0 (control), 10 and 20% (w/w) and mixed thoroughly. Plastic pots were filled with called mixture (2 kg). The experimental layout consisted of split-plots were arranged in a completely randomized design with three replicates. The results showed that with increasing sludge from 0 to 10 and 20%, the wheatgrass germination decreased significantly (P≤0.05). In alfalfa and flax, no significant differences were observed in seed germination percentage among petroleum sludge treatments. The mean values of plant heights and root and shoot dry weights for wheatgrass in 20% petroleum sludge showed a significant reduction when compared with control. By increasing the amounts of petroleum sludge from 0 to 20%, Root and shoot dry weights decreased by 46.6 and 93.3% in alfalfa and 41.1 and 82.2% in flax respectively. Although both alfalfa and flax have higher germination capability in comparison with wheatgrass but they showed less biomass production. Therefore, cultivation of alfalfa and flax is not recommended for petroleum phytoremediation, explicitly due to lower biomass production. In brief, wheatgrass could be a suitable species for phytoremediation of sludge petroleum, as this plant produces more roots than shoots and more fibrous root systems.